1. Field of the Invention
This invention relates to an improved method for treating contact lenses.
2. Description of the Related Art
While using contact lenses, dirt in the environment, microorganisms, proteins in tear liquid and the like attach to the lenses during wearing and eyes are hurt by them when the contact lenses are worn for a long time. Therefore, it is necessary to sterilize and wash the lenses periodically, preferably, every day.
It has been known that hydrogen peroxide can be effectively used for sterilizing and washing contact lenses. It is also known that the remaining hydrogen peroxide in the treating liquid after the treatment irritates and hurts eyes when the lenses thus treated are worn again and therefore, the remaining hydrogen peroxide must be removed.
There have been already proposed various means for removing hydrogen peroxide in processes for treating contact lenses with hydrogen peroxide. For example, U.S. Pat. No. 3,829,329 discloses boiling in a distilled water and normal saline solution. Such boiling is, however, inconvenient to the user and deteriorates contact lenses. Japanese Patent Application Laidopen Nos. Sho 59-105,457 and Sho 60-70,416 disclose that hydrogen peroxide is decomposed by using sodium pyruvate and sodium sulfite, respectively, as a reducing agent. In these methods the reducing agent should be used in the stoichiometrical amount or more, so that it is complicated to weigh the reducing agent and further the remaining reducing agent and the resulting oxidized product are contained in the treating liquid, and therefore, these compounds may adversely affect eyes. In addition, U.S. Pat. No. 4,414,127 discloses water-soluble inorganic salts or organic salts, in particular, copper sulfate, as a hydrogen peroxide decomposing catalyst, but even when such catalyst is used, metal ions are contained in the treating liquid so that it is difficult to avoid any adverse effect on eyes.
On the other hand, Japanese Patent Application Publication No. Sho 53-14,243 disclosed metallic catalysts for decomposing hydrogen peroxide, in particular, platinum black carrying catalyst. According to this method, indeed any problems found in the above-mentioned patents do not occur and this method appears to be good, but the platinum black carrying catalyst is produced by coating chloroplatinic acid on a carrier and reducing it, so that the production process is very complicated, and further the platinum black is easily peeled off from the carrier and lost by mechanical contact resulting in short life. Therefore, this method neither gives a satisfactory result.